It is contemplated by this invention to provide a means for rapidly bringing a ring laser into operative condition, even at very low temperatures, in a minimum time after turn-on. Prior ring lasers, which used a cold cathode and at least one anode to supply an electric field and electrons to the laser gas discharge, required on the order of at least 300 milliseconds after the exciting voltage was applied between such cathode and anodes before the laser was ready to operate as an angular rate sensor. At times such discharge could not be obtained. It is contemplated by this invention to illuminate the cold cathode of the ring laser to reduce the start-up time, even at very low temperatures, to the order of three to eight milliseconds.
Although no prior art of illuminating ring laser cold cathodes is known to the inventor, radiation rays have been used in linear lasers for purposes other than accelerating the start-up of the laser.
Radiation rays have also been used in connection with arc and glow lamps and with tubes.
Examples of the background art known to the inventor follow.
U.S. Pat. No. 2,405,071, which pertains to a Pulse Generating System, shows in FIG. 1 an ultra violet source used to illuminate a spark gap in air. As recited in column 3, line 75 to column 4, line 7, the purpose of irradiating the spark gap is to enhance the accuracy of timing of the firing intervals of the spark.
U.S. Pat. No. 3,224,236, which pertains to a Noble Gas Flash Lamp and Laser Light Source, describes an explodable chemical light source characterized by high brilliancy, high color temperature, and special and specific spectral emission qualities. Such flash lamp sources have particular spectral characteristics to match those of a laser which is to be pumped. The high intensity flashing light is then used to pump the laser, raising the energy levels of the laser gas so that the gas lases.
U.S. Pat. No. 3,351,870, which pertains to a Pulsed Gas Laser, teaches a linear laser having a continuous operation. The laser gas is a mixture of helium and neon, and the gas is pumped by high voltage repetitive pulses each having fast rise time, short width and relatively long pulse repetition rate. Alternatively, it is recited that the laser may be energized by direct current or radio frequency energy. Column 12, line 68 through column 13, line 1 recites that although use of a cold cathode from which electrons are emitted by gamma processes and field emission were described, the electrons may be supplied by a hot cathode, or the electrons may be given off as a result of ultraviolet light impinging upon a cold cathode and producing photoelectric emission of electrons.
U.S. Pat. No. 3,657,600 pertains to Auxiliary Ionization of DC Electric Discharge Electrode Boundary Sheaths particularly in high power lasers such as nitrogen/carbon dioxide lasers. The invention uses auxiliary ionization of gas plasma in a column of anode-cathode ion and electron flow in the nitrogen/carbon dioxide. One of the auxiliary ionization sources, as recited in column 4, lines 66 through 71, is a source of intense photon flux oriented to inject flux adjacent to either or both of the main electrodes of the DC electric discharge. When the auxiliary ionization is employed in a gas laser, the photon flux should preferably be of a wavelength which does not interfere with laser operation.
U.S. Pat. No. 3,772,608, which pertains to Charged-Particle Discharge for a Laser, teaches the use of a radioactive source to produce charged particles which are injected throughout the discharge volume of a laser to create uniform ionization therein and thus trigger the electrical discharge needed to excite the laser medium. The beam of charged particles initiates a discharge by producing an initial ion and electron population within the discharge volume. The charged particle beam may be created by a radioactive source or by artificial sources such as electron guns, particle accelerators, or other devices which produce a directed flow of charged particles with sufficient energy to penetrate the active laser fluid over the entire discharge volume.
U.S. Pat. No. 3,934,212 pertains particularly to a high powered pulsed laser--for example, a carbon dioxide laser. The patent discloses a laser comprising a volume of gas having a lasing constituent, a light source arranged to emit light having ionizing photons for ionizing the gas, with the effective photon energy spectrum of the ionizing photons lying below the ionization potential of the lasing constitutent and below the level of photon absorption bands of the gas.
U.S. Pat. No. 4,004,250 pertains to Laser Action by Optically Depumping Lower States. The invention is directed to depopulating lower energy levels of a high powered laser, typically of the carbon dioxide type, by exposing the laser medium (carbon dioxide) to an intense source of radiation. The radiation must have particular wavelength characteristics to achieve the required depumping.
U.S. Pat. No. 4,016,448 pertains to a High Power Electric Discharge Method and Apparatus for Laser Chemical Synthesis and Other Applications. The type of an external ionization source 70 is not specified. It is mentioned only once in column 6, line 60. The plasma instability growth time is approximately CP/JE where P is the gas pressure in Torr, JE is the electrical power density in watts/cubic centimeter and the constant C is increased in amplitude when the external ionization source is used. Thus the plasma instability growth time is increased by a factor of ten by using the external ionization source.
U.S. Pat. No. 4,064,465 pertains to Laser Cavities with Gas flow through the electrodes. The apparatus is particularly directed toward a high pressure pulsed gas laser wherein the laser gas is flowing at high pressure through an electrode assembly. Discharge initiation is achieved using, for example, ultraviolet irradiation of the electrode assembly. U.S. Pat. No. 4,077,017 pertains to an Ultraviolet Radiation Induced Discharge laser. The laser is a high pressure gas pulsed laser, such as a transverse electric atmosphere laser, to achieve free electron production in the gas by photoelectric interaction between ultraviolet radiation and a cathode prior to the gas-exciting cathode-to-anode electrical discharge, thereby producing volume ionization of the gas.